Alkali treated starch and process for making same



Patented Nov. 26,

UNITED srATE I ALKALI TREATED s'rancn ANDYPROCESS FOB. Maxine SAME Gerald John Leuck, Evanston, 111., assignor to Corn Products Refining Company, New York. N. Y., a corporation New Jersey N0 Drawing.

This invention relates to the modification of starch and its object is to provide a novel process whereby starch may be given a .high fluidity, when in paste form, without substantially increasing its solubility in cold water. a.-

The process involves treatment' of the starchwith analkali at hydrogen ion concentrations substantially above pH '7, at relatively high temperatures for relatively long periods of time and w in the presence of a small amount of water. The preferredalkaline substance is ammonia but other alkaline substances may be used.

The invention is applicable to all the common starches, such as corn, potato, wheat, rice and 15 tapioca starches.

Th alkaliused is preferably a volatile'lihuid 25 division. {The alkalied starch or the present invention may, however, be used for other purposes. I Thinboiling starches are ordinarily made by heating starch in'suspension in water containing 30 a small amount of acid. Starch treated in this manner, if reacted with formaldehyde, does not give a water resistant product. It is less waterresistant than a reaction product of formaldehvde and raw starch, in fact. 35 It has been customary to treat starch in suspension in water with an alkali, without heating,

to bring about' gelat'inization or the starch. It the mixture of starch, water and alkali having a pH above '7 is heated sufliciently,.decomposi= 4o sition of thestarch takes place indicated by formation'of dark color and reduction in hot paste. viscosity; and the starch no longer has the characteristic amylose properties. It has also beenvcustomary to treat starch-water sus- 45 pensions with alkalies-at hydrogen ion'concentrations below pH 7, the mixture being heated as in the production of thin boilings arch. The purpose or the alkali treatment in such case is to bring about gelatinization oi tlm starch.

so The process of the present invention is diflerent from all or the above processes and results in a characteristically different product, namely, one which may be reacted with tormaldehyde to give a compound which, when set or solidified, will be 55 adhesive, cohesivepand substantially water-in.-

Application December 15,1938, Serial No. 245,907

2 Claims. (01. 127-33) I soluble. According to the present process the starch is heated for a considerable period of time with a suflicient amount of alkali to maintain the pH throughout the heating period at a point substantially above the neutral point, and in the presence of a very limited amount of moisture; an amount large enough to insure the type of conversion required, that is to furnish the required hydroxyl ions but not sufficient to give a water medium for carrying the hydroxyl ions or to gelatinize the starch. The water is present, not as aliquid, but in the form of vapor or of water fllms, or both. In thisistate the hydroxyl ions are not sufliciently active to change the starch into decomposition products. The prod- 1 uct remains essentially starch, with the usual amylose characteristics. Not being gelatinized the product is not in any sense a .cold water swelling starch. That is, when put int cold water,-it is not changed into a gelatinous state through adsorption of water, as is the case with so-called cold water swelling starches.

The fluidity of its paste when-boiled with-water is increased. Its solubility is slightly but not substantially or, proportionally increased. The starch has the peculiar and novel characteristic o! reacting with formaldehyde to give a water resistant compound.

The presence of some. water is necessary. If

dry starch mixed with an alkali, added in sufficient amounts so that the mixture'never becomes acidic, is roasted at ordinary dextrinizing temperatures, no reaction takes place at all comparable to the'dextrinization which occurs when starch is'roasted in the esence of an acid. In 5 tact under dry conditio of operation at relatively lower temperatures no reactiontakes place at all; and at extremely high temperatures the starch is decomposed but is not in any sense dextrinized. Heating dry starch mixed with an 40 alkali in a dry atmosphere will not give a product having the characteristics sought forby the present invention. The treatment 01' the starch according to the present invention involves some increase in solubility accompanying the increase in fluidity. In the dextrinization of starch the increase or fluidity is accompanied by a very large increase of. solubility, the solubilities of dextrine ranging from 2% to 100% 4r thereabout. What is intended by the statement made herein that, in the present process, the fluidity or the starch is increased without substantial increase in solubility, is that the increase in solubility is very small a in relation to the increase influidity, in compari- 66 ten, ieiinstance, with the increase of solubilities taking place along with increased fluidities in the dextrinizatlon processes.

Preferably in carrying out the process of this 6 invention the water is added to the starch little by little in order to prevent the formation 01" liquid medium in the material and the undesired activity of the hydroxyl ions; and the alkali is also added gradually as the treatment progresses, 10 so as to maintain the pH during substantially the entire treatment substantially above the neutral point. Y

The invention will be illustrated in' the following specific examples which are to be considered as merely typical and informative and not as limiting the invention to the particular operating data therein given. The intentionJs to claim all equivalents as well as all modifications withzo in the scope of the appended claims.

Example 1 1000 parts by weight of powdered raw com I starch having a moisture content of approxil mately 10% is placed in a dextrine cooker of the usual type equipped with a fairly tight have: and the material is then treated with moisture and ammonia as follows: 3.5 parts of ammonia gas is injected gradually, in the course of an hour, with 80 continuous stirring, into the cooker, so that the starch is thereby made definitely alkaline. Heat .is then applied so that the temperature of the starch is gradually raised to a maximum of approximately 300 F. in the course of eight hours,

as and the starch is maintained at approximately this temperature for an additional fifteen hours.

1 After the temperature of the starch has passed 212 F., the boiling point of water, additional ammonia, and water in the form of steam, are injected into the cooker, at such a rate as to maintain an excess of each of these constituents in the atmosphere, within the cooker. This con-i ditlon of excess moisture is satisfied, for example, when the moisture continues to condense on the inside of the cooker lid. Continuedevolution of steam witha strong odor of ammonia,

passing through-a small vent provided in thecooker lid, iszevidence that the condition of excess of both-of these constituents is being mainso tained. Stirring is continued throughout theheating period.

Subsequent to the first addition of ammonia the starch should always test purple to the pa:

indicatedwill ordinarilysufiice'ifthe cooker is.

fairly tight to maintain moisture and ammoniaat high enough concentrations. A After the heat treatment is finished the charge is broulht to room temperature in acooler andsieved in a reel 'li'iaccording to ordinary dextrine mahuiectuiihg practice. obtained is a powder of a light} yellow-brown color. Itsfluidilm-whm in theform orepastewmhemuehhigherthahthe fluidity of the raw starch treated. The cold u olubility win her be in pronbrueh.

perature for sixteen hours before I trample 2 p 100 parts of powdered raw corn starch having an ordinary air dry moisture content 0110'5-155 is placed in a horizontal cylinder which is closed except for a gas aperture at each end. Am- 5 moniagasattherateof lpartperhourisbubbled. through water, held at a temperature near its boiling point, and the gas thus moistened is continuously passed through the cylinder, whichis continuously revolved as a means of mixing the m ingredients. As soon as there isan odor of ammonia at the exit aperture heat is applied to the cylinder at such a rate that the starch reaches a temperature of approximately 284' I. in 2 to 3 hours; The treatment is then continued at this maximum temperature with the addition of moistened ammonia gas for, sixteen hours longer. The product obtained upon cooling is similar in appearance and properties to the product of the dextrine cooker described in Example 1. '9

Example 3 1500 parts of powdered raw corn starch from 'which the free or absorbed moisture has previ- "I ously been substantially removed by drying to a constant weight at'2,12 F. is mixed thoroughly with parts, of 28% aqueous ammonia and is then introduced into an autoclave. perature within the autoclave is gradually ina Thetemcreased ,at such a rate that in two hours the charge reaches a maximum temperature of approximately 275 F. and a maximum gauge pressure of approximately 50 pounds per square inch. The charge is maintained at approximately this 35 I temperature and pressure for seven hours and is then .allowedto cool.

Example 4 1000 parts of powdered raw corn starch hav- 40 ing a moisture content of approximately 5% is placed in the dextrine cooker described in Example '1. Thesubsequent procedure of alkaline treatmentis the sameasthatdescrlbedinExample 1 except that time and tempu'ature con- 4s ditions are difleren't in the following respects: After the of the application ofheat, the temperature of; the starch is gradually raised to 335 1''. in the course ofinine hours and is thereafter maintained at approximatelythi'stem- 50 perature for an additional five hours (instead of asinExample Lattitiningamaximumtunperatureof3001".inthecourseofeighthour's) and is thereafter maintained at for flfteenhours. i as t Examples partsofpowderedairdrypotatostuchis 7 thoroushly'ml'xedwith iopartsofasqi aqueous ammonia andthe mix'tureis placed in an autoclove. Thematerialisgraduallyralsedtdatemperatureof250? 1".andmaintainedatthlstemi samples Th procedure hereisthesameasinlxample 4 oi'mtthattlietimeandtemperatureconditions during the alkaline treatment are diiferuit application of heat,thetemperatureofthestarch 10 is gradually raised 1:0 :35 I. in the coune ofsevenhours and is thereafter maintained at-approximately this temperature for an sevenhours.w Thisprocedureyieltkaprodmfof dre tera idit the the'pmdu terhiii ie4.u-

When referenceis made to parts, it is understood that parts'by weight is intended. I

In all of the examples given above, the alkali treatment provides'a means for modifying the starch so that its fluidity is increased without substantial increase of cold-water solubility. A

raw corn starch possessing a (one part of the starch heated pasted in parts of water) relative fluidity of 4 cc. (volume of paste flowing.

the raw starch, and a cold water solubles content of only 1.9%. According to this A method of testing for fluidity the above mentioned raw starch would have zero fluidity. Upon subjecting raw corn starch of the character above mentioned to the alkali treatment described in Example 4, the product has been found to have a relative fluidity of cc. and a solubles content of 1.3%. Upon subjection of a like ,raw starch to the alkali treatment described in-Example 6, the product has been found to have a 54 relative fluidity 01 75, while the cold water solubles content has risen to only 3.7%. Thus,

in accordance with the present invention, the fluidity of the starch may be very greatly increased without substantial increase in its cold water solubility as above defined.-

I claim:

1. Process of treating starch to increase its fluidity without substantial increase of its cold water solubility which comprises: heating the starch to a temperature of approximately 335 for a period of 14 to 24 hours in the presence of steam in an amount insuflicient to gelatinize the starch but sumcient to-provide hydroxyl ions and ammonia inamount to keep the material at a pH above 7. v

2. An alkali treated starch product characterized in that: it is ungelatinized; it contains substantially no amylose decomposition products; it has a higher fluidity than raw starch and a cold water solubility which is not substantially higher than that of raw starch; and it reacts with formaldehyde at a pH not substantially above 2 to form a water resistance compound.

GERALD JOHN muck. 

